Abstract Our understanding of subduction initiation remains limited by the difficulty of making direct observations of geologically recent examples. In the geologic record, supra‐subduction zone ophiolites are often interpreted to record syn‐initiation slab rollback and upper plate extension. Unfortunately, many ophiolites are decoupled from records of subsequent arc maturation and/or lack robust geochronological constraints. In this contribution, we investigate the initiation of the Late Triassic‐Jurassic Talkeetna Arc of southern Alaska. The Talkeetna Arc is one of the world's preeminent examples of an oceanic magmatic arc, yet the timing and tectonic record of its initiation remain unconstrained. Our study integrates geologic mapping with a chemostratigraphic analysis of ∼3.5 km of pillow basalts that comprise the Lower Shuyak Formation (Kodiak Archipelago, Alaska). The Lower Shuyak Formation hosts Late Triassic calc‐alkaline plutons and is overlain by ∼2 km of volcaniclastic strata. Initial mafic volcanism was characterized by high‐Ti, E‐MORB‐like tholeiites that are enriched in high field strength elements (HFSEs) and light rare earth elements. Compositions transition up section to HFSE/LREE‐depleted island arc tholeiites that become enriched in Th. These trends are consistent with petrologic processes during subduction initiation. High‐precision U‐Pb zircon dates (CA‐ID‐TIMS) constrain initiation to ∼232 Ma or slightly earlier. Our results demonstrate that initiation of the Talkeetna Arc occurred earlier than previous estimates, slightly preceding the eruption of regionally extensive flood basalts interpreted by previous studies as plume‐related. This relationship may suggest that subduction initiation was plume‐induced, or that rifting of the upper plate was the primary driver of basaltic volcanism regionally.

Abstract We welcome the critique of Hetényi and Cattin (2026, https://doi.org/10.1029/2025tc009214 ) on Sternai et al. (2025, https://doi.org/10.1029/2025tc009057 ), as it brings to light evaluative issues that require clarification and offers an opportunity to articulate more clearly how our work advances understanding of Himalayan‐Tibetan geodynamics. In this Reply, we clarify that most of the criticism arises from evaluating our process‐oriented geodynamic models as if they were intended to reproduce present‐day lithospheric structures, rather than to test the mechanical plausibility of Paleogene crustal‐doubling mechanisms. Moreover, non‐unique interpretations of present‐day geophysical data are treated in the Comment as definitive constraints and used as benchmarks to dismiss alternative physically viable scenarios, leading to circular reasoning. When the content and objectives of our study are correctly considered, the critiques do not invalidate our results or conclusions. More broadly, this Reply underscores the importance of reassessing established models when fundamental limitations are identified, as a constructive pathway toward progress in Earth sciences.

Abstract Crustal thinning and hyperextension have been clearly imaged and well‐documented in the Qiongdongnan Basin (QDNB), located in the NW South China Sea. Integrated analysis of newly acquired 3D seismic data, covering the majority of the QDNB, reveals the presence of two distinct fault systems: a NE‐trending set and an E‐W‐trending set, both of which played significant roles in controlling sedimentation patterns and crustal deformation during Cenozoic rifting. The NE‐trending faults were primarily active during a first stage (∼42.5–33.9 Ma) and led to crustal stretching. In contrast, the E‐W‐trending faults developed during a second stage (∼33.9–25.5 Ma) and induced crustal necking and hyperextension, resulting in the formation of metamorphic core complexes and associated detachment faults. Kinematic restoration of seismic profiles indicates that detachment fault activity and crustal thinning progressed through a gradual westward migration during the second stage. This evolution followed a core complex necking model, wherein ductile lower crustal material flowed into the footwall region beneath the detachment fault, thereby expanding the exhumation domain until the lower crust in the hanging wall was fully attenuated. Subsequently, fault deformation transitioned from decoupled to coupled behavior, with strain progressively localizing within the brittle upper crust of the hanging wall, ultimately resulting in the formation of a hyperextended crustal architecture.

Abstract Understanding how spatially variable mountain‐building processes proceed within large intracontinental orogens provides critical insights into continental tectonics and regional paleoenvironmental evolution. Here, we address this issue in the central South Tian Shan (cSTS), a key transitional segment between the well‐studied eastern and western South Tian Shan. This region is characterized by extensive glaciation, peaks exceeding 6,000 m, complex drainage patterns, and the active range‐front Maidan Fault, highlighted by the recent M w 7.0 Wushi earthquake. We integrate seismic profile interpretation, kinematic forward modeling, and geomorphic analysis to reconstruct the multi‐spatiotemporal deformation history of the Eastern Wushi foreland. Our results show that basinward propagation of the Wushi foreland thrust system began at ∼5.3 Ma, significantly later (by 10–15 Ma) than in adjacent segments. GPS velocity data and deformed Late Quaternary geomorphic surfaces at the Wushi foreland indicate ongoing activity along the eastern Maidan Fault, with total active shortening across the Eastern Wushi foreland estimated at ∼2.0–3.3 mm/yr over the past ∼30 Kyr. Together, these findings suggest an active transpressional mountain‐building regime in the cSTS, characterized by oblique slip along the range‐front Maidan Fault, coeval foreland deformation, and potential shear thickening of the orogenic wedge. Our results reveal that the South Tian Shan accommodates crustal shortening through spatially variable mountain‐building processes, highlighting the coexistence of transpressional and in‐sequence thrust wedge processes across the range. This differential mountain building provides new insights into the evolution of active intracontinental orogens on a thousand‐kilometer scale.

Abstract Accretionary complexes are key archives of subduction zone processes, preserving records of forearc growth, deformation, and tectonic reorganization. The Chugach–Kodiak accretionary complex of southern Alaska records Jurassic to Cretaceous underplating at shallow to intermediate subduction conditions. The McHugh Complex, an imbricated sequence of prehnite–pumpellyite facies oceanic and trench‐derived rocks forms a major component of this subduction margin. We present new structural data, U–Pb detrital zircon geochronology, zircon (U–Th)/He thermochronology, and Raman spectroscopy of carbonaceous material from two regional transects across the McHugh on the Kenai Peninsula. In the structurally highest thrust panels, maximum depositional ages young trenchward from 169 to 148 Ma, consistent with downward growth by underplating. A 54 Myr gap (148–94 Ma) is interpreted to bracket a period of subduction erosion. A similar gap 200 km to the northeast, attributed by previous studies to Early Cretaceous ridge subduction, suggests that this erosional event was regionally extensive. Accretion resumed by 95 Ma and involved re‐entrainment of Jurassic material. Zircon (U–Th)/He thermochronology shows that most of the McHugh remained buried until Paleocene exhumation, coincident with regional ridge subduction. The McHugh complex is organized into 2–4 km thick duplexes bounded by mélange shear zones interpreted as paleo–subduction interfaces. Coherent thermal histories within duplex panels, and temperature jumps across thrusts, suggest underplating of lenses with distinct thermal histories, later tilted and exhumed intact. These results provide new constraints on how accretionary margins evolve through alternating episodes of underplating, erosion, and forearc unroofing.

No abstract is available for this article.

Abstract The Cenozoic crustal deformation characteristics and underlying mechanisms in the southeastern Tibetan Plateau (TP) are critical for constraining tectonic models of plateau growth during this era. Paleomagnetic analyses and U–Pb zircon dating were conducted on the syenite pluton and adjacent sandstones in the Jianchuan Basin (26°38′43″N, 99°49′18″E), located at the southeastern margin of the TP. The site‐mean direction obtained from syenite rocks is D = 7.1°, I = 42.9°, k = 88.6, α 95 = 7.2° at 35.54–33.14 Ma and the tilt‐corrected site‐mean direction obtained from the sandstones is D s = 17.5°, Is = 43.4°, k = 141.0, α 95 = 3.1° at 28.0–24.0 Ma. Combined with Cenozoic paleomagnetic data sets from regions surrounding the Eastern Himalayan Syntaxis (EHS), the results indicate that although clockwise rotational crustal deformation initiated at the southeastern margin of the TP around ∼28.0 Ma, no significant latitudinal displacement has occurred since then. In contrast, the central and southeastern TP have experienced significant northward crustal convergence since the Late Eocene, relative to the reference poles of the Tarim and Qaidam Basins. These contrasting patterns of crustal movement suggest that the convergence between India and Asia has not led to substantial lateral crustal escape from the southeastern TP since the Oligocene, and that the ongoing northward migration of the EHS represents the primary driving force that quasi‐synchronously caused the southeastern margin of the TP to undergo significant clockwise crustal rotational deformation while maintaining a stable latitudinal position since approximately 28.0–24.0 Ma.

Abstract The Ilyak fault in Tajikistan is an E‐W striking strike‐slip fault, which forms the northern boundary of the actively deforming Tajik Basin fold and thrust belt. Determining the activity of the Ilyak fault is important for understanding the hazard to the nearby capital city of Dushanbe, and more generally in assessing the role of lithology in controlling fault behavior. Using a bespoke Multi‐Temporal InSAR approach with 5 years of Sentinel‐1 satellite radar acquisitions, we produce regional surface velocity maps with a horizontal spatial resolution of 130 m and numerical uncertainties below 1 mm/yr. Our rate maps reveal previously unrecognized details of creep, fault structure, and slip partitioning. We document creep on the Ilyak fault with a right‐lateral rate of 8.1–8.7 mm/yr in the east reducing to 4.2–4.5 mm/yr in the west, as slip is progressively transferred to adjacent folds and thrusts in the Tajik Basin. Creep on the Ilyak fault and adjacent thrusts appears to be controlled by lithology, in particular the presence of evaporite‐rich layers. Nonetheless, moderate earthquakes within the basement beneath the Ilyak fault, including a destructive M5.5 event in 1989, suggest potential earthquake hazards from deeper crustal layers. Using high‐resolution Digital Elevation Models derived from optical stereo satellite data we document fault scarps north of the Ilyak fault, which may constitute an additional source of hazard. Filtered velocity maps also show evidence of soil creep and active, slow‐moving landslides across the basin and in the mountains, constituting another hazard to local communities and infrastructure.

Abstract The Altai Accretionary Wedge in the Mongolian Altai records a polyphase geodynamic evolution involving two extensional–compressional tectonic cycles, constrained by petrostructural analysis and zircon, monazite U–Pb, and Ar–Ar geochronology. The studied section includes a southwestern high‐grade and a northeastern low‐grade domain, previously considered suspect terranes. However, U–Pb zircon data indicate that both represent the same Cambrian–Ordovician tectonostratigraphic unit, variably overprinted by Devonian and Permian magmatism and metamorphism. The first cycle involved Devonian extension that produced subhorizontal fabrics in both domains, accompanied by widespread magmatism dated at 410−362 Ma. These fabrics were later folded into upright, N–S‐trending Carboniferous folds, preserved mainly in shallow crustal levels. In the high‐grade domain, this event was associated with medium‐pressure to medium‐temperature metamorphism 500−560°C, 5.5−7.5 kbar dated at 358−335 Ma. The second cycle began with the development of a crustal‐scale detachment that juxtaposed the two domains. This extensional event triggered melting of Devonian lower crust and emplacement of granite plutons in the upper crust. It was further characterized by medium‐pressure to high‐temperature metamorphism 715−785°C, 5−8 kbar and formation of subhorizontal extensional mylonites, constrained to 320−278 Ma. Continued extension produced a core complex in the southwestern domain, exhumation of partially molten lower crust, and synchronous deposition of clastic sediments onto the detachment. Subsequent compression caused strong N–S shortening and steepening of earlier fabrics, constrained by Ar–Ar muscovite and biotite ages of 268−245 Ma. Consequently, the Mongolian Altai–Trans‐Altai boundary is redefined as a verticalized extensional‐detachment zone.

Abstract Syn‐to late‐orogenic extension caused by gravitational collapse is a process that has been documented in most orogens. In this paper, we investigate the contemporaneous stress field in Taiwan to examine syn‐orogenic extensional faulting and the possible gravitational collapse modes by which it is taking place. We use a new, large, well‐constrained, clustered earthquake focal mechanism data set from which we calculate the stress field ( σ 1 , σ 2 , σ 3 ), the direction of the maximum compressive horizontal stress ( S H ), and determine the most likely fault plane orientations and kinematics. Our results show that, in the upper 21 km of the crust, shearing, with lesser compression are the dominant stress regimes in the Western Foothills and Hsuehshan Range, resulting in a complex interaction of strike‐slip (with transpression and transtension) and thrust faulting. Extension is predominately localized in the upper 14 km of the crust in the Central Range (CR), where it is roughly orogen‐parallel. S H and the best‐fit fault planes in the CR strike roughly NW‐SE, at a high angle to the structural and topographic grain. At depths greater than 21 km, compression and shear, with transpression and minor extension are the dominant stress regimes throughout Taiwan. Along the eastern flank of the mountain belt, mixed compression and shear stress regimes at depths greater than 50 km are related to the Manila and Ryukyu subduction zones. Our new results allow, for the first time, to characterize an ongoing, large‐scale, orogen‐parallel extension in Taiwan related to lateral extrusion with free‐boundary gravitational collapse.